We all love our trees and shrubs. They soften the landscape of our neighborhoods, green our city, and offer numerous aesthetic and environmental benefits. These benefits can easily be lost without proper care. Trees will succumb to the stresses of the harsh urban and suburban environment. Poor or compacted soil, limited root space, pollution, and competition with turf grass are just a few examples of the challenges trees face. These stresses weaken defense mechanisms and lead to poor growth rates, dieback in crown, and open the door to insect damage and decay. To help your trees and shrubs to maintain vigor and overcome environmental stresses, it is essential that your trees be well fed. Nutrient availability is the key.
In the natural setting, trees have unlimited root space, a decomposing layer of leaves and fallen debris, called humus, that create a nutrient cycle constantly feeding the tree, and do not have to compete with turf grasses for nutrients and water. However, the trees in our yards and parks are missing the nutrient cycling. Limited root space means our trees have to do more from less space. Fall leaf collections remove the much needed humus layer. And the competition with turf grass means even fewer nutrients are available to the trees. Although mulching does helps tremendously, most trees only have 10% of the tree’s rooting zone covered. The vast majority of feeder roots miss out on the benefits of mulching. To compensate for these deficiencies, trees need fertilization.
Proper fertilization of trees means we must get the right amount of nutrients (nitrogen, phosphorus, and potassium) to the right location. Soil sampling and analysis provide the amount of macro and micro nutrients that are needed. With the results from a soil analysis, an arborist can create a fertilizer mix tailored to the specific soil and trees involved.
To get the nutrients to the trees, the tree’s feeder roots are the target. Most tree feeder roots exist in the top 18 inches of the soil and extend beyond the dripline of the tree’s canopy. Broadcast and surface applied fertilizers are often absorbed by turf grass before they reach the feeder roots, or are lost through runoff before they can be utilized by trees. The solution is a deep-root fertilization which directly injects nutrients to the tree’s roots, bypassing turf grass or other ground covers and greatly reducing runoff losses.
Deep Root Fertilization
Deep-root fertilization is the most effective way to fertilize trees and shrubs. 
This process injects a water and slow release fertilizer mixture under high pressure 2 to 18 inches below the soil surface, right to where the feeder roots are. The fertilizer is injected on a 3ft by 3ft grid pattern throughout the tree’s root zone to ensure even coverage and availability. The high pressure injection forces the water fertilizer mixture throughout the root zone which feeds all the roots and helps to reduce soil compaction.
In addition to the nitrogen, phosphorous, and potassium, several products can be added to compliment the fertilizer. Micronutrients such as Iron can be added to correct iron deficiencies, which causes a yellowing of leaves. Mycorrhiziae, a beneficial fungus, attach to roots to increase feeder roots’ ability to uptake water and nutrients. Finally root growth hormone is added to stimulate root growth in newly planted trees and mature trees showing signs of weakness.
Keeping your trees and shrubs healthy and vigorous is our goal. The arborists at Woodland Tree Service are more than happy to evaluate your trees and shrubs and apply deep-root fertilization to help your plants meet there full potential.
If you need any assistance with your trees, please contact the experts at Woodland Tree Service. Email joanna@woodlandtree.com or call us at (901) 309-6779.